The present invention relates to medical cannulas and more particularly to soft cannulas and obturators therefor.
Arthroscopy cannulas and mating obturators have traditionally been manufactured from rigid materials such as metals or rigid polymers. The cannula has a smooth inside diameter and the obturator has a smooth outside diameter. To insert the cannula into a patient, the obturator is placed into the cannula. The cannula/obturator is them “pushed” into the patient thru a small stab incision or portal.
Several potential issues exist with traditional rigid cannulas and obturators. Because they are rigid, they can be somewhat traumatic to the patients tissues. Additionally, as the patients joint swells with fluids during arthroscopy the cannulas tend to become loose in the portal and sometimes back out. Recently, several silicone (or other soft material) cannulas have been commercialized which attempt to address the existing limitations of rigid cannulas. However, the soft material has introduced new limitations.
The force required to insert cannula/obturator typically increases when the transition between the cannula and obturator reaches the patients skin. As the rigid cannula is introduced with increasing force to overcome such resistance it retains its shape due to its rigidity. However, soft and flexible cannulas cannot be inserted into a joint by the traditional means of inserting a obturator inside them and pushing them into the joint. When this is attempted, the soft, flexible cannula “accordions” on the obturator when its distal end hits the external skin. This problem is particularly evident when attempting to insert silicone cannulas which have a distal flange to prevent the cannula from backing out.
The typical method for inserting a silicone cannula with a distal flange is to grasp the distal end of the cannula with forceps, compress the distal flange and “jam” the cannula into the joint via the distal end. Thus, the cannula is pulled in from the distal end, not pushed in from the proximal end. This is an awkward insertion method that causes increased trauma to the portal site and often results in an enlarged portal.